This invention relates generally to airbag modules with integrated gas generation. More specifically, this invention relates to airbag modules that do not require a discrete inflator or a discrete filter.
The standard airbag module comprising a cover, a base-plate or reaction container, an inflatable cushion which is folded in the undeployed state, and a discrete gas generator or inflator is well known in the art.
Traditional airbag module assembly processes usually install the discrete gas generator after the airbag module is substantially assembled. The reason is that gas generators are typically related as stand alone assemblies and can comprise a housing containing an igniter, a gas generating compound, a combustion chamber, a filter, and output orifices. However, these conventional gas generators could be activated by an electrical signal and produce gas without being physically installed in the airbag module. Thus, in actual practice, they are handled with special countermeasures to reduce any risks of activation during the shipping and handling of the assemblies.
Another aspect of existing gas generators is that they may use orifices that are drilled in radial or slightly off-axis radial directions that allow the gas to be projected only in radial or near radial directions. In some gas generator assemblies, additional parts, known as diffusers, are used in combination with the gas generator to project the gas flow into a desired direction. The drawback to these gas generators is that the radial projection of the gas flow of these gas generators will make the gas impinge onto surfaces directly outside the inflator housing, such as the surface of a diffuser or the fabric of an airbag cushion. When the gas jet is stopped by these surfaces, a local area of high pressure and high temperature is created which may cause high structural stress and/or abrasion of the surface.
Another aspect of existing gas generators is that they may use external parts, such as diffusers, to alter the properties of the gas flowing from the gas generator during inflation into more favorable properties for flow into an airbag cushion. However, such diffusers require a certain volume to alter the gas properties for which space must be made available between the gas generator and the airbag cushion.
Existing gas generators may use specially shaped pellets to create a gas flow more suitable for direct flow into an airbag cushion.
Existing gas generators also may use internal heat sinks to alter the properties of the gas, especially in the initial stage of the gas generation process. However, the heat sinks in existing gas generators require additional space and require careful dimensioning to avoid rattles.
Furthermore, existing gas generators are characterized in that they have one volume of high pressure, generally in the combustor chamber, which determines the flow of gas. The exit port holes are dimensioned to sustain the oxidization process in the combustor chamber. These gas generators require a flow path of constantly decreasing pressure to sustain the flow.